JP6109324B2 - Motor drive control device, compressor, blower, and air conditioner - Google Patents

Description

  The present invention relates to a motor drive control device, a compressor, a blower, and an air conditioner.

  As a conventional motor drive control device, there is one that generates a DC bus voltage for driving an inverter from an AC power source such as a commercial power source by a rectifier circuit. Such a motor drive control device is used as a drive source of a motor such as a compressor of an air conditioner, for example.

  In such cases, the motor tends to be designed so that the induced voltage (counterelectromotive force) and the power supply voltage are approximately the same around the rated speed for the purpose of improving energy consumption efficiency in rated operation. is there. During overload operation that causes the motor to operate at a rotational speed that exceeds the rated rotational speed of the motor, the output current of the inverter circuit increases due to saturation of the output voltage of the inverter circuit. A decrease or the like will occur.

  Therefore, in order to suppress such a decrease in operating efficiency, a motor drive control device including a booster circuit has been proposed (see, for example, Patent Document 1). The booster circuit is provided between the rectifier circuit and the inverter circuit, and includes a reactor, a backflow prevention diode, and a switching element. The DC bus voltage rectified by the rectifier circuit is boosted by the booster circuit. In the booster circuit, energy is stored in the reactor during the ON period of the switching element, and the stored energy is released during the OFF period of the switching element, whereby the DC bus voltage is boosted. The boosting of the DC bus voltage in the boosting circuit is controlled by the time (on duty) during which the switching element is turned on. By boosting the DC bus voltage in the booster circuit, the voltage applied to the motor is increased and the current applied to the motor is suppressed, thereby improving the driving efficiency and expanding the driving range.

  In such a motor drive control device, when the boosting operation of the booster circuit is performed, the operation efficiency is lowered due to the circuit loss caused by the driving of the switching element. Therefore, the boosting operation of the booster circuit is performed only in the operation region where boosting is necessary.

JP 2012-196142 A (paragraph [0012] to paragraph [0059], FIGS. 1 to 16)

  In such a motor drive control device, when the start-up operation of the boosting operation of the booster circuit is started and the DC bus voltage is boosted toward the target voltage at a fast voltage change rate, the motor rotation When the number increases, a steep current flows on the AC power supply side, and the controllability of the harmonic countermeasure device such as the active filter and the controllability of the booster circuit are deteriorated. Also, for example, when the responsiveness of the detection circuit is low, such as when the modulation degree of the inverter circuit is calculated by detecting the DC bus voltage, an excess voltage is applied to the motor and an overcurrent flows. there is a possibility. Also, when the DC bus voltage is increased toward the target voltage and the voltage change rate is slow, if the motor speed increases, the voltage required to drive the motor cannot be obtained, and the motor Overcurrent will flow through the. That is, there is a problem that a stable operation cannot be secured in the start operation and stop operation of the boost operation of the boost circuit.

  The present invention has been made against the background of the above-described problems, and provides a motor drive control device that ensures a stable operation in the start-up operation and stop operation of the booster circuit. Moreover, the compressor, air blower, and air conditioning apparatus which use such a motor drive control apparatus are obtained.

A motor drive control device according to the present invention includes a rectifier that rectifies an AC voltage supplied from an AC power supply, a reactor, a switching element, and a backflow prevention element, and boosts the DC bus voltage supplied from the rectifier. A circuit, a smoothing capacitor that smoothes the output of the booster circuit, an inverter circuit that converts the DC bus voltage smoothed by the smoothing capacitor into an AC voltage and supplies the AC voltage, and controls the operation of the booster circuit Boost control means, inverter control means for controlling the operation of the inverter circuit, and a DC bus voltage detector for detecting a DC bus voltage supplied from the boost circuit, the boost control means comprising the inverter control based on the degree of modulation of the conversion to the AC voltage from the DC bus voltage at the unit performs a start operation or stop operation of the boost operation, Serial inverter control means, between said boost control means is made to perform a boosting operation to said boosting circuit, when the DC bus voltage supplied from the booster circuit is increasing, the set rotational speed of said motor The inverter circuit is operated so as to be fixed.

  In the motor drive control device according to the present invention, the inverter control means is configured so that the rotation speed of the motor is fixed while the boost control means causes the boost circuit to start the boost operation or stop the boost operation. Operate the inverter circuit. Therefore, a stable operation in the start operation and stop operation of the boost operation of the boost circuit is ensured.

It is a figure which shows the structure of the motor drive control apparatus which concerns on Embodiment 1, and the structure of the air conditioning apparatus using the same. It is a figure which shows the structure of the pressure | voltage rise control means of the motor drive control apparatus which concerns on Embodiment 1. FIG. FIG. 5 is a diagram illustrating a time chart of a boosting operation of the motor drive control device according to the first embodiment. FIG. 5 is a diagram illustrating a time chart of a boosting operation of the motor drive control device according to the first embodiment. It is a figure which shows the flow of determination of the start of boost operation | movement of the motor drive control apparatus which concerns on Embodiment 1, and a stop. It is a figure which shows the time chart in case the setting rotation speed reduces during the voltage change of the pressure | voltage rise operation | movement of the motor drive control apparatus which concerns on a comparative example. It is a figure which shows the time chart in case the setting rotation speed increases during the voltage change of the pressure | voltage rise operation | movement of the motor drive control apparatus which concerns on a comparative example. FIG. 5 is a diagram illustrating a time chart of a boosting operation of the motor drive control device according to the first embodiment. It is a figure which shows the flow of the stop operation | movement of the pressure | voltage rise operation of the motor drive control apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the flow of the stop operation | movement of the pressure | voltage rise operation of the motor drive control apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the time chart of the pressure | voltage rise operation | movement of the motor drive control apparatus which concerns on a comparative example. FIG. 5 is a diagram illustrating a time chart of a boosting operation of the motor drive control device according to the first embodiment.

Hereinafter, a motor drive control device according to the present invention will be described with reference to the drawings.
In the following, a case is described in which the motor drive control device according to the present invention drives a motor used in a compressor of an air conditioner, but the motor drive control device according to the present invention is not limited to this. It may drive a motor used in the device. Further, the configuration, operation, and the like described below are merely examples, and the motor drive control device according to the present invention is not limited to such a configuration, operation, and the like. In addition, descriptions or illustrations of detailed structures, operations, etc. are simplified or omitted as appropriate. In addition, overlapping or similar descriptions are appropriately simplified or omitted.

Embodiment 1 FIG.
A motor drive control device according to Embodiment 1 will be described.
<Configuration of motor drive control device>
The configuration of the motor drive control device according to the first embodiment will be described below.

FIG. 1 is a diagram showing a configuration of a motor drive control device according to Embodiment 1 and a configuration of an air conditioner using the same.
As shown in FIG. 1, the motor drive control device 1 converts the power supplied from the three-phase AC power supply 6 and supplies it to the motor (load M) of the compressor 2 of the air conditioner 200. The motor drive control device 1 includes a three-phase rectifier 10, a booster circuit 20, a smoothing capacitor 30, and an inverter circuit 40. In the air conditioner 200, the compressor 2, the condenser 3, the expansion device 4, and the evaporator 5 are connected by a refrigerant pipe to form a refrigerant circulation circuit. The motor drive control device 1 may drive the motor of the blower 7 that supplies air to the condenser 3. Further, the blower 7 may supply air to the evaporator 5.

  The three-phase rectifier 10 converts an AC voltage (for example, AC 200 V) of the three-phase AC power source 6 into a DC bus voltage. The three-phase rectifier 10 is, for example, a three-phase full-wave rectifier in which six diodes are bridge-connected.

  The booster circuit 20 is a circuit (boost chopper circuit) that boosts the DC bus voltage from the three-phase rectifier 10 to, for example, DC 350V. The step-up circuit 20 includes a reactor 21, a switching element 22, and a backflow prevention element 23. The operation of the booster circuit 20 will be described in detail later.

  As the switching element 22 and the backflow prevention element 23, for example, a wide band gap semiconductor such as a silicon carbide (SiC) element, a gallium nitride (GaN) -based element, a diamond element, etc. having a larger band gap than a silicon (Si) element. Should be used. In addition to the wide band gap semiconductor, a semiconductor element such as a MOFET or an IGBT may be used as the switching element 22. Further, an element such as a fast recovery diode may be used as the backflow prevention element 23.

  The smoothing capacitor 30 smoothes and charges the output from the booster circuit 20.

  The inverter circuit 40 converts DC power charged in the smoothing capacitor 30 into AC power (PWM voltage). The inverter circuit 40 is composed of a plurality of switching elements. The switching element is, for example, an IGBT. As the switching element of the inverter circuit 40, a wide bandgap semiconductor such as a silicon carbide (SiC) element may be used as in the switching element 22 described above. The inverter circuit 40 is connected to the motor of the compressor 2 of the air conditioner 200 and supplies an alternating current having a predetermined frequency to the motor of the compressor 2.

  Further, the motor drive control device 1 includes a DC bus voltage detection unit 51, a motor current detection unit 52, and a reactor current detection unit 53. The DC bus voltage detection unit 51 detects the DC bus voltage Vdc that is the output voltage from the booster circuit 20 by measuring the voltage of the smoothing capacitor 30. The motor current detector 52 detects the current supplied from the inverter circuit 40 to the motor of the compressor 2. Reactor current detection unit 53 detects reactor current IL flowing through reactor 21.

  In addition, the motor drive control device 1 calculates an inverter control means 60 that controls the operation of the inverter circuit 40, a boost control means 70 that controls the operation of the booster circuit 20, and a target rotational speed n of the motor of the compressor 2. A target rotational speed calculation unit 80, a boost operation start determination unit 90, and a boost operation stop determination unit 100 are provided. The inverter control means 60, the boost control means 70, the target rotational speed calculation means 80, the boost operation start determination means 90, and the boost operation stop determination means 100 are executed by, for example, a program module in response to a command from the CPU of the microprocessor unit. To be built.

(Target speed calculation means)
The target rotational speed calculation means 80 calculates the target rotational speed n of the motor of the compressor 2 that can obtain a desired refrigeration capacity from information such as the outside air temperature, the set temperature, and the pressure, and sets the target rotational speed n to the inverter control means 60. Output. The target rotational speed calculation means 80 updates the target rotational speed n output to the inverter control means 60 at intervals of several seconds to several tens of seconds. With such a configuration, the control stability of the air conditioner 200 is improved.

(Inverter control means)
The inverter control means 60 controls the inverter circuit 40 (PWM control) based on the DC bus voltage Vdc detected by the DC bus voltage detector 51 and the current detected by the motor current detector 52.

  The inverter control means 60 sets the rotational speed of the motor of the compressor 2 based on the target rotational speed n calculated by the target rotational speed calculating means 80 (the rotational speed is described as a set rotational speed N). . The inverter control means 60 controls the motor of the compressor 2 by adjusting the frequency of the output voltage of the inverter circuit 40 to be equal to the set rotational speed N. Normally, the set rotational speed N is set to a value equal to the target rotational speed n. When the rotation speed fixing control described later is performed, the set rotation speed N is set to a value different from the target rotation speed n. In the following description, the case where the boosting operation of the booster circuit 20 is controlled based on the set rotational speed N of the motor of the compressor 2 will be described. However, based on the current value of the motor current detector 52 and the like, The number of rotations of the motor may be detected, and the boosting operation of the booster circuit 20 may be controlled based on the detected value.

  Specifically, inverter control means 60 determines the frequency of the output voltage of inverter circuit 40 based on the product of set rotational speed N and the number of motor pole pairs. Further, the inverter control means 60 acquires a voltage command value based on the current detected by the motor current detection unit 52 and the set rotational speed N, and the voltage command value and the DC bus voltage detection unit 51 detect the voltage command value. The modulation degree K is calculated from the DC bus voltage Vdc using the following equation (1) to calculate the time for turning on each switching element of the inverter circuit 40 (generates a PWM signal). Since the voltage command value and the rotation speed of the motor of the compressor 2 are in a substantially proportional relationship, the voltage command value is controlled to increase as the set rotation speed N of the motor of the compressor 2 increases.

(Boosting control means)
FIG. 2 is a diagram showing the configuration of the boost control means of the motor drive control device according to the first embodiment.
As shown in FIG. 2, the boost control means 70 includes target voltage setting means 74a, voltage command value calculation means 74b, current command value calculation means 74c, and switching signal generation means 74d.

  The target voltage setting means 74a presets and stores a target voltage value for the DC bus voltage Vdc supplied from the booster circuit 20 during the boosting operation (the target voltage value is described as a final target voltage value). The final target voltage value will be described in detail later.

  The voltage command value calculation means 74b calculates a voltage command value based on the final target voltage value set by the target voltage setting means 74a and the DC bus voltage Vdc detected by the DC bus voltage detector 51. Proportional integral control (PI control) or the like can be used for the voltage command value calculation means 74b.

  The current command value calculation unit 74c calculates a switching command value based on the voltage command value calculated by the voltage command value calculation unit 74b and the reactor current IL detected by the reactor current detection unit 53. Proportional integral derivative control (PID control) or the like can be used for the current command value calculation means 74c.

  The switching signal generating unit 74d generates a switching signal SS for driving the switching element 22 based on the switching command value calculated by the current command value calculating unit 74c. The switching signal SS is a driving pulse (PWM command), and a switching command value is applied to a carrier wave (for example, a triangular wave) having a predetermined frequency, and a large period compared to the switching command value is turned on. Moreover, it produces | generates by converting a small period compared with the switching command value into an OFF state.

(Boosting operation start determination means)
The boosting operation start determining unit 90 determines whether or not to start the boosting operation of the boosting circuit 20 and outputs the result to the boosting control unit 70. The step-up operation start determining unit 90 determines whether to start the step-up operation of the step-up circuit 20 using a step-up operation start condition described in detail later.

(Boosting operation stop judgment means)
The step-up operation stop determining unit 100 determines whether to stop the step-up operation of the step-up circuit 20 and outputs the result to the step-up control unit 70. The step-up operation stop determination unit 100 determines whether to stop the step-up operation of the step-up circuit 20 using a step-up operation stop condition A and a step-up operation stop condition B, which will be described in detail later.

<Operation of motor drive control device>
The operation of the motor drive control device according to the first embodiment will be described below.

(Boost circuit operation)
The operation of the booster circuit 20 will be described below.

  An AC voltage is supplied from the three-phase AC power source 6 to the three-phase rectifier 10 and is rectified to a DC voltage by the three-phase rectifier 10. When the booster circuit 20 is performing a boosting operation, the DC voltage rectified by the three-phase rectifier 10 is boosted by the booster circuit 20. In the booster circuit 20, when the switching element 22 is turned on, the conduction of the backflow prevention element 23 is blocked, and the voltage rectified by the three-phase rectifier 10 is applied to the reactor 21. On the other hand, when the switching element 22 is turned off, the backflow prevention element 23 becomes conductive, and a voltage opposite to that when the switching element 22 is turned on is induced in the reactor 21. That is, when the switching element 22 is turned on, energy is accumulated in the reactor 21, and when the switching element 22 is turned off, the accumulated energy is transferred to the inverter circuit 40 that is a load. be able to. Then, by controlling the on-duty of the switching element 22, the DC bus voltage Vdc of the booster circuit 20 is controlled. On the other hand, when the booster circuit 20 is not in the boosting operation, the switching element 22 is not turned on and energy is not stored in the reactor 21, so that the DC voltage rectified by the three-phase rectifier 10 is not boosted.

  The booster circuit 20 performs a boost operation when the motor of the compressor 2 is in a driving state, that is, when the inverter circuit 40 is operating. Therefore, in the initial state, the booster circuit 20 does not perform the boosting operation.

(Determination of start of boost operation)
Hereinafter, determination of the start of the boosting operation will be described.

  As the set rotational speed N of the motor of the compressor 2 increases, the output voltage of the inverter circuit 40 needs to be increased. However, when the three-phase rectifier 10 is used as in the motor drive control device 1, if the boosting operation of the booster circuit 20 is not performed, the output voltage of the inverter circuit 40 is the AC of the three-phase AC power supply 6. Limited by voltage. Therefore, an operation region in which the output voltage of the inverter circuit 40 is saturated occurs, and when the set rotational speed N of the motor of the compressor 2 is increased in such a state, the current flowing through the motor of the compressor 2 increases. Thus, the motor loss (copper loss) of the compressor 2 increases. In order to suppress such a phenomenon, in the motor drive control device 1, in the overmodulation region where the output voltage of the inverter circuit 40 is saturated (the operation region where the modulation degree K> 1), the booster circuit 20 is being boosted. To do. By controlling in this way, the voltage applied to the motor of the compressor 2 becomes high and the current flowing through the motor of the compressor 2 is suppressed, so that the operation efficiency is improved.

  Further, when the booster circuit 20 is performing a boosting operation, losses (switching loss, conduction loss, etc.) are generated by the switching operation of the switching element 22 and the backflow prevention element 23. On the other hand, in particular, when the motor of the compressor 2 is stopped, when the set rotational speed N of the motor of the compressor 2 is low, or when the operating range is a modulation degree K <1, the output of the inverter circuit 40 The voltage is not saturated, and there is no need to perform the boosting operation of the booster circuit 20. Therefore, in the motor drive control device 1, the boosting operation of the boosting circuit 20 is performed only in the operation region where the boosting operation of the boosting circuit 20 needs to be performed.

  That is, the motor drive control device 1 starts the boosting operation of the booster circuit 20 only when either of the following formulas (2) and (3) is satisfied (when the boosting operation start condition is satisfied). The determination as to whether or not either of the expressions (2) and (3) is satisfied is performed by the boosting operation start determining means 90.

  According to Expression (2), the boosting operation of the booster circuit 20 is performed and the output voltage of the inverter circuit 40 is increased only in the operation region where the output voltage of the inverter circuit 40 is saturated. Further, according to the expression (3), it is possible to suppress that the harmonic component included in the current supplied from the three-phase AC power supply 6 affects the operation of the motor of the compressor 2 in a specific operation region. Become. That is, in the current command value calculation unit 74c of the boost control unit 70, the difference between the voltage command value calculated by the voltage command value calculation unit 74b and the reactor current IL detected by the reactor current detection unit 53 is eliminated. Since the switching command value is calculated, when the booster circuit 20 is performing the boosting operation, the reactor current IL is controlled to be a constant value. Therefore, by performing the boosting operation of the boosting circuit 20, the current supplied from the three-phase AC power supply 6 can be made into a rectangular wave shape, and the influence of the harmonic component included in the current can be suppressed. And it is desired to suppress the influence of the harmonic component by defining the operation region where the influence of the harmonic component is to be suppressed by the relationship between the set rotational speed N of the motor of the compressor 2 and the predetermined value by the expression (3). It is possible to suppress the influence of harmonic components only in the operation region.

(Overview of boosting operation start and stop operation)
The outline of the start operation and stop operation of the boost operation will be described below. The details of the start operation and stop operation of the boost operation will be described later.

FIG. 3 is a diagram illustrating a time chart of the boosting operation of the motor drive control device according to the first embodiment.
Before and after the boosting operation of the booster circuit 20 is started and stopped, each output changes as shown in FIG.

  When the boosting control means 70 receives a boosting operation start command of the boosting circuit 20 from the boosting operation start determining means 90, the boosting control means 70 starts switching of the switching element 22 until the final target voltage value set by the target voltage setting means 74a. The DC bus voltage Vdc is boosted. The final target voltage value is set in advance in consideration of the maximum rotational speed of the motor of the compressor 2, the motor loss of the compressor 2, the circuit loss of the motor drive control device 1, and the like. The final target voltage value may be a constant value. In addition, the target voltage setting means 74a has an optimum final target voltage value at which the total of the motor loss of the compressor 2 and the circuit loss of the motor drive control device 1 is the lowest for each set rotation speed N of the motor of the compressor 2. May be stored in the form of a table, and the tabulated information may be used to switch to the final target voltage value corresponding to the set rotational speed N of the motor of the compressor 2.

  The step-up control means 70 may step up the DC bus voltage Vdc to the final target voltage value set by the target voltage setting means 74a in a state where the step-up speed is not controlled, and changes with time. The voltage may be boosted in a state where the boosting speed is controlled by the target voltage value.

  That is, as shown in FIG. 3, the target voltage value for the DC bus voltage Vdc supplied from the booster circuit 20 at the start of the boost operation start operation is used as the DC bus voltage detection unit immediately before the start of the boost operation start operation. The DC bus voltage Vdc detected by 51 may be set, and the target voltage value may be gradually increased to the final target voltage value as time elapses from the start of the boost operation start operation. In such a case, sudden changes in voltage and current are suppressed, and control stability is improved. In such an operation, the on-duty of the switching element 22 becomes 0 (switching stopped) at the start of the boost operation start operation, and gradually increases with the passage of time from the start of the boost operation start operation. Will increase. It is preferable that the amount of voltage change per unit time of the target voltage value (voltage change slope) can be set freely. The speed of increasing the on-duty of the switching element 22 changes according to the voltage change amount.

  Further, as shown in FIG. 3, the target voltage value for the DC bus voltage Vdc supplied from the booster circuit 20 at the start of the stop operation of the boost operation is used as a DC bus voltage detection unit immediately before the start of the stop operation of the boost operation. It may be set to the DC bus voltage Vdc detected by 51, and the target voltage value may be gradually decreased with the passage of time from the start of the boost operation stop operation. Even in such a case, a rapid change in voltage and current is suppressed, and control stability is improved. In such an operation, the on-duty of the switching element 22 gradually decreases with the passage of time from the start of the boost operation stop operation, and finally becomes 0 (switching stop). It is preferable that the amount of voltage change per unit time of the target voltage value (voltage change slope) can be set freely. According to the voltage change amount, the on-duty reduction rate of the switching element 22 changes.

(Judgment of stopping boost operation)
Hereinafter, determination of stop of the boosting operation will be described.

  As shown in Expression (1) and FIG. 3, the modulation degree K decreases as the DC bus voltage Vdc increases. Therefore, since the expression (2) is not established when the booster circuit 20 performs the boost operation start operation, whether or not to stop the booster operation of the booster circuit 20 is determined. If the determination is made under the conditions used for determining whether or not to start the control, the control becomes unstable. Therefore, the motor drive control device 1 stops the boosting operation of the booster circuit 20 when the following conditions (boost operation stop condition A or boost operation stop condition B) are satisfied.

FIG. 4 is a diagram illustrating a time chart of the boosting operation of the motor drive control device according to the first embodiment.
As shown in FIG. 4, when the start operation of the boosting operation is started at t1, the DC bus voltage Vdc reaches the final target voltage value at t2, and the start operation of the boosting operation is completed, the modulation factor K at that time Is temporarily stored (the modulation degree K is described as a reference modulation degree Ks).

  As the reference modulation degree Ks, the timing at which the DC bus voltage Vdc detected by the DC bus voltage detector 51 coincides with the final target voltage value set by the target voltage setting means 74a, that is, the modulation degree K at t2 is stored. The timing after the DC bus voltage Vdc detected by the DC bus voltage detector 51 matches the final target voltage value set by the target voltage setting means 74a for a predetermined period (about several seconds), That is, the modulation degree K at t3 may be stored. When the modulation degree K at t3 is stored, it is possible to suppress erroneous detection of the completion of the start-up operation of the boosting operation due to voltage overshoot, noise, or the like.

  Further, at the same timing as the reference modulation degree Ks, the set rotational speed N of the motor of the compressor 2 is temporarily stored (the set rotational speed N is described as the reference set rotational speed Ns). As the reference set rotational speed Ns, as described later, the timing at which the start operation of the boosting operation is started, that is, the set rotational speed N at t1 may be stored.

  The motor drive control device 1 stops the boosting operation of the booster circuit 20 when at least one of the following formulas (4) and (5) is satisfied (when the boosting operation stop condition A is satisfied). The determination as to whether or not at least one of Expression (4) and Expression (5) is satisfied is performed by the boosting operation stop determination means 100. It is good also as conditions on satisfying both a formula (4) and a formula (5). In such a case, stability of control is improved.

  By the expression (4), the stop of the start operation of the boost operation due to the failure of the above expression (2) is suppressed, and the start operation of the boost operation is surely performed in the operation region where the output voltage of the inverter circuit 40 is saturated. It becomes. Further, in the equation (5), the set rotational speed N of the motor of the compressor 2 is smaller than a value obtained by subtracting the hysteresis amount Nshys (for example, about several percent of Ns) from the reference set rotational speed Ns. In this case, it is specified that the boosting operation of the booster circuit 20 is stopped. The stability of the control when the boosting operation of the booster circuit 20 is started by satisfying the above-described expression (3) is improved by the expression (5).

  Further, the motor drive control device 1 stops the boosting operation of the booster circuit 20 when the following formula (6) is satisfied (when the boosting operation stop condition B is satisfied). Whether or not the expression (6) is satisfied is determined by the boosting operation stop determination unit 100.

  Expression (6) indicates that the boosting operation of the booster circuit 20 is stopped when the set rotational speed N of the motor of the compressor 2 is smaller than the preset boosting operation forced stop rotational speed Noff. It prescribes. For example, when the voltage of the three-phase AC power supply 6 drops more than expected, the formula (2) is satisfied even though the boosting operation of the booster circuit 20 is not required to be performed. Even if the boosting operation of the booster circuit 20 is started, the boosting operation of the booster circuit 20 is forcibly stopped by the equation (6). Therefore, the reliability of the air conditioning apparatus 200 is improved.

(Flow of determination of start and stop of boost operation)
In the following, the flow for determining the start and stop of the boosting operation will be described.

FIG. 5 is a diagram illustrating a flow of determination of start and stop of the boosting operation of the motor drive control device according to the first embodiment.
As shown in FIG. 5, in step S101, the boosting operation stop determination unit 100 determines that the set rotational speed N of the motor of the compressor 2 at that time is smaller than the preset boosting operation forced stop rotational speed Noff. Or not, that is, whether or not Expression (6) is satisfied. When Expression (6) is not satisfied, the process proceeds to S102, and when Expression (6) is satisfied, the process proceeds to S109.

  In S102, the boosting operation start determining means 90 determines whether the modulation degree K calculated at that time by the inverter control means 60 is larger than 1, that is, whether or not the expression (2) is satisfied, and the compressor It is determined whether or not the set rotational speed N of the motor No. 2 at that time is larger than a predetermined value set in advance, that is, whether or not Expression (3) is satisfied. If at least one of Expression (2) and Expression (3) is satisfied, the process proceeds to S103, and if not, the process proceeds to S109.

  In step S103, the boosting operation start determination unit 90 sends a start-up command for starting the boosting operation to the boosting control unit 70, and the process proceeds to step S104. The boosting control means 70 sets the target voltage value to the DC bus voltage Vdc detected by the DC bus voltage detecting unit 51 immediately before receiving the start command for starting the boost operation, and the start command for starting the boost operation is set. The target voltage value is gradually increased until the final target voltage value is reached as time elapses from the time of receipt.

  In S104, the boosting operation stop determination unit 100 determines whether or not the DC bus voltage Vdc detected at that time by the DC bus voltage detection unit 51 has reached the final target voltage value set by the target voltage setting unit 74a. Determine. If it has reached, the process proceeds to S105, and if not, the process returns to S103.

  In step S105, the boosting operation stop determination unit 100 stores the modulation degree K calculated at that time by the inverter control unit 60 as the reference modulation degree Ks, and also sets the rotational speed N of the motor of the compressor 2 at that time. Is stored as the reference set rotational speed Ns, and the process proceeds to S106.

  In step S106, the boosting operation stop determination unit 100 determines whether the modulation degree K calculated at that time by the inverter control unit 60 is smaller than the reference modulation degree Ks, that is, whether or not the expression (4) is satisfied. Whether or not the set rotational speed N of the motor of the compressor 2 at that time is smaller than the value obtained by subtracting the hysteresis amount Nshys from the reference set rotational speed Ns, that is, whether or not the formula (5) is satisfied. Determine. If at least one of the expressions (4) and (5) is not satisfied, the process proceeds to S107. If both the expressions (4) and (5) are satisfied, the process proceeds to S109.

  In S107, the boosting operation stop determining unit 100 sends a boosting operation continuation command to the boosting control unit 70, and the process proceeds to S108.

  In S108, the boosting operation stop determining unit 100 determines whether or not the set rotational speed N of the motor of the compressor 2 at that time is smaller than the preset boosting operation forced stop rotational speed Noff, that is, the equation (6). ) Is satisfied. When Expression (6) is not satisfied, the process returns to S106, and when Expression (6) is satisfied, the process proceeds to S109.

  In S109, the boosting operation start determining unit 90 or the boosting operation stop determining unit 100 sends a boosting operation stop command start command to the boosting control unit 70, and the process returns to S101. The boost control means 70 sets the target voltage value to the DC bus voltage Vdc detected by the DC bus voltage detector 51 immediately before receiving the start command for the boost operation stop operation, and issues a start command for the stop operation of the boost operation. As the time elapses from the time of receipt, the target voltage value is gradually decreased.

(Details of boost operation start operation)
The details of the boost operation start operation will be described below.

  FIG. 6 is a diagram illustrating a time chart when the set rotational speed decreases during voltage change in the voltage step-up operation of the motor drive control device according to the comparative example. FIG. 7 is a diagram illustrating a time chart when the set rotational speed increases during voltage change in the voltage step-up operation of the motor drive control device according to the comparative example.

  After the start of the boost operation, the DC bus voltage Vdc detected by the DC bus voltage detector 51 reaches the final target voltage value set by the target voltage setting means 74a, that is, t1 to t2. When the set rotational speed N of the motor of the compressor 2 increases or decreases during the voltage change during the period, the modulation degree K changes in conjunction with the voltage command value, that is, the set rotational speed N.

  For example, as shown in FIG. 6, when the set rotational speed N of the motor of the compressor 2 decreases during the voltage change between t1 and t2, the reference modulation degree Ks used for the determination of the stop of the boosting operation described above. However, the boosting operation is continued in spite of being an operation region in which the boosting operation is unnecessary, that is, an operation region in which the output voltage of the inverter circuit 40 is not saturated. The operating efficiency of the harmony device 200 is reduced.

  Further, for example, as shown in FIG. 7, when the set rotational speed N of the motor of the compressor 2 increases during the voltage change between t1 and t2, the reference modulation used for the determination of the stop of the boosting operation is performed. The degree Ks becomes larger than the original value, and the boosting operation is stopped despite the operation region where the boosting operation is necessary, that is, the operation region where the output voltage of the inverter circuit 40 is saturated. Become. Further, when the voltage change amount per time (the slope of the voltage change) of the target voltage value is set large, the set rotational speed N of the motor of the compressor 2 during the voltage change between t1 and t2. Increases, a steep current flows through the three-phase AC power supply 6 and the controllability of the harmonic countermeasure device such as the active filter and the controllability of the booster circuit 20 are deteriorated. Further, when the voltage change amount per time (the slope of the voltage change) of the target voltage value is set small, the set rotational speed N of the motor of the compressor 2 during the voltage change between t1 and t2. Increases, the increase in the output voltage of the inverter circuit 40 cannot follow the increase in the set rotational speed N, and the motor current of the compressor 2 may increase, leading to an overcurrent state.

FIG. 8 is a diagram illustrating a time chart of the boosting operation of the motor drive control device according to the first embodiment.
Therefore, the motor drive control device 1 fixes the set rotational speed N of the motor of the compressor 2 during the voltage change between t1 and t2, as shown in FIG. .) Then, at t2 or t3, after the reference modulation degree Ks is stored, the rotational speed fixing control is canceled to update the set rotational speed N, and the rotational speed of the motor of the compressor 2 is increased or decreased. In addition, in order to fix the setting rotational speed N of the motor of the compressor 2, in addition to the case where the setting rotational speed N of the motor of the compressor 2 is fixed at a state where it does not increase or decrease at all, the setting rotational speed of the motor of the compressor 2 is set. The case where the number N is fixed to a state where the above-described problem is not increased or decreased is included.

  In addition, the target rotational speed calculation means 80 calculates the target rotational speed n at regular intervals so that a desired refrigeration capacity can be obtained at any time. Therefore, the inverter control means 60 performs only storage during the rotation speed fixed control, that is, between t1 and t2 or between t1 and t3, even if a new target rotation speed n is input. The set rotation speed N is not updated. Then, at t2 or t3, after the aforementioned reference modulation degree Ks is stored, the set rotational speed N is updated to the stored target rotational speed n.

(Details of stop operation of boost operation)
Details of the stop operation of the boosting operation will be described below.

  In a state where the booster circuit 20 starts the boost operation stop operation and gradually decreases the target voltage value as time elapses from the time when the boost operation stop operation start command is received, Even if the DC bus voltage Vdc detected by the bus voltage detector 51 drops and the set rotational speed N of the motor of the compressor 2 decreases, the power consumption is reduced. And an excessive electric current does not flow into the motor of the compressor 2. Therefore, when the DC bus voltage Vdc detected by the DC bus voltage detection unit 51 tends to decrease and the set rotational speed N of the motor of the compressor 2 tends to decrease, it is necessary to perform rotational speed fixing control. There is no.

FIG. 9 is a diagram illustrating a flow of the stop operation of the boosting operation of the motor drive control device according to the first embodiment.
That is, as shown in FIG. 9, when the boost control means 70 receives a start command for stopping the boost operation, in S201, the boost control means 70 determines whether or not the boost circuit 20 is operating. If it is in operation, the process proceeds to S202, and if not, the process proceeds to S206.

  In S202, the boost control means 70 determines whether or not the DC bus voltage Vdc detected at that time by the DC bus voltage detector 51 is increasing. If it is rising, the process proceeds to S203, and if not, the process proceeds to S204.

  In step S203, the boost control unit 70 transmits a command to the inverter control unit 60 to turn on the rotation speed fixing control, and the process returns to step S201.

  In S204, the boost control means 70 determines whether or not the DC bus voltage Vdc detected at that time by the DC bus voltage detection unit 51 is decreasing. If it is descending, the process proceeds to S205, and if not, the process proceeds to S206.

  In S205, the boost control means 70 determines whether or not the set rotational speed N of the motor of the compressor 2 is decreasing. When it is not decreasing, it progresses to S203, and when it is decreasing, it progresses to S206.

  In step S206, the boost control unit 70 transmits a command to the inverter control unit 60 so that the rotation speed fixing control is turned off, and the process returns to step S201.

  Further, during the period from when the reference modulation degree Ks is stored between t2 and t4 or between t3 and t4 in FIG. 3 until the step-up operation is started, the DC bus voltage detection unit 51 detects it. In the case where the DC bus voltage Vdc is kept constant, if the set rotational speed N of the motor of the compressor 2 is the same, the modulation degree K is also substantially the same value according to the equation (1). Therefore, when the stop operation of the boosting operation is started, Equation (4) is already satisfied and then Equation (5) is satisfied, so that the set rotational speed N of the motor of the compressor 2 tends to decrease. Can be guessed. Therefore, the determinations in S204 and S205 in FIG. 9 may be omitted.

FIG. 10 is a diagram illustrating a flow of the stop operation of the boosting operation of the motor drive control device according to the first embodiment.
That is, as shown in FIG. 10, when the boost control means 70 receives an instruction to start the boost operation, it determines whether or not the boost circuit 20 is operating in S301. If it is in operation, the process proceeds to S302; otherwise, the process proceeds to S304.

  In S302, the boost control means 70 determines whether or not the DC bus voltage Vdc detected at that time by the DC bus voltage detection unit 51 is increasing. If it is rising, the process proceeds to S303, and if not, the process proceeds to S304.

  In step S303, the boost control unit 70 transmits a command to the inverter control unit 60 to turn on the rotation speed fixing control, and the process returns to step S301.

  In step S304, the boost control unit 70 transmits a command to the inverter control unit 60 so that the rotation speed fixing control is turned off, and the process returns to step S301.

(Reference rotation speed Ns and reference modulation degree Ks)
The reference set rotational speed Ns is stored at t2 or t3, that is, the set rotational speed N of the motor of the compressor 2 at the time when the boosting operation start operation is completed. However, when the DC bus voltage Vdc is increased in the start-up operation of the boosting operation, the rotational speed fixing control is in the ON state, so the set rotational speed N is a constant value between t1 and t2 or between t1 and t3. become. Therefore, the reference set rotational speed Ns may be stored at t1, that is, the set rotational speed N of the motor of the compressor 2 at the time of starting the boosting operation start operation. By being operated in this way, the following effects can be obtained.

  First, the case where the reference set speed Ns is t2 or t3, that is, when the set speed N of the motor of the compressor 2 is stored at the time when the start operation of the boosting operation is completed will be described.

FIG. 11 is a diagram illustrating a time chart of the boosting operation of the motor drive control device according to the comparative example.
As shown in FIG. 11, for example, when the set rotational speed N of the motor of the compressor 2 is decreased at t5 during the pressure increasing operation after t2, and satisfies the equations (4) and (5), at t6 Then, the boosting operation of the boosting circuit 20 is started. When the power supply voltage of the three-phase AC power supply 6 becomes lower than that before the start of the boost operation start operation, the DC bus voltage Vdc detected by the DC bus voltage detection unit 51 is t1, that is, the start of the boost operation. The value is lower than the value at the time of starting the operation, and the expression (2) is satisfied at t7. As a result, the start operation of the boosting operation is started again.

  At this time, if the reference set speed Ns is t2 or t3, that is, the set speed N of the motor of the compressor 2 is stored at the time when the start operation of the boosting operation is completed, at t8, That is, in the process in which the DC bus voltage Vdc detected by the DC bus voltage detection unit 51 is raised to the final target voltage value, both the expressions (4) and (5) are satisfied, and The stop operation of the boost operation is started. That is, at t8, the set rotational speed N of the motor of the compressor 2 does not change, so that Expression (5) is satisfied. Further, since the modulation degree K calculated by the inverter control means 60 is compared with t2 or t3, that is, the reference modulation degree Ks stored at the time when the start operation of the previous boosting operation is completed, at t8, Equation (4) is satisfied. That is, the start command for the boost operation and the start command for the stop operation are repeated in a state where the start operation of the boost operation is not completed, and the hunting is performed on the DC bus voltage Vdc detected by the DC bus voltage detector 51. Will occur.

  Next, the case where the reference set speed Ns is t1, that is, the set speed N of the motor of the compressor 2 stored at the time of starting the boosting operation will be described.

FIG. 12 is a diagram illustrating a time chart of the boosting operation of the motor drive control device according to the first embodiment.
As shown in FIG. 12, when the reference set rotational speed Ns is t1, that is, when the set rotational speed N of the motor of the compressor 2 is stored at the time of starting the boost operation start operation, at t7 When the start operation of the boosting operation is activated again, the reference set rotational speed Ns is updated. As a result, at t8, Expression (5) is not satisfied, and the boost operation stop operation of the booster circuit 20 is not started. Therefore, occurrence of hunting in the DC bus voltage Vdc detected by the DC bus voltage detection unit 51 is suppressed. The reference modulation degree Ks is updated at t9 or t10, that is, when the start operation of the boosting operation is completed again.

  Further, the above-described reference set rotational speed Ns and reference modulation degree Ks may be initialized at t6, that is, when both of the expressions (4) and (5) are satisfied, and the operation is performed as such. In addition, the same effect as described above can be obtained.

<Operation of motor drive control device>
The operation of the motor drive control device according to Embodiment 1 will be described below.
In the motor drive control device 1, the inverter control unit 60 is configured so that the rotation speed of the motor is fixed while the boost control unit 70 causes the booster circuit 20 to start the boost operation or stop the boost operation. By operating the inverter circuit 40, the amount of voltage change (gradient of voltage change) per unit time of the DC bus voltage Vdc, which is the output voltage from the booster circuit 20, in the start operation of the boost operation or the stop operation of the boost operation. It can be changed and set freely. Therefore, the stability of the control of the harmonic countermeasure device such as the active filter and the control of the booster circuit 20 is ensured. For example, by setting the voltage change amount so as to reach the final target voltage value in about several seconds, it is possible to suppress the ability as the air conditioner 200 from being affected.

  Further, the boosting operation start determining unit 90 and the boosting operation stop determining unit 100 determine the start of the boost operation start operation and the start of the boost operation stop operation based on the reference modulation degree Ks and the reference set rotation speed Ns. It is ensured that the boosting operation is performed only in the necessary operation region, and the operation efficiency is improved. Further, the inverter control means 60 sets the inverter circuit 40 so that the rotation speed of the motor is fixed while the boost control means 70 causes the boost circuit 20 to start the boost operation or stop the boost operation. Due to the synergistic effect with the operation, it is further ensured that the stable operation in the start-up operation and the stop operation of the boost circuit 20 is ensured.

  DESCRIPTION OF SYMBOLS 1 Motor drive control device, 2 Compressor, 3 Condenser, 4 Throttling device, 5 Evaporator, 6 Three-phase alternating current power supply, 7 Blower, 10 Three-phase rectifier, 20 Booster circuit, 21 Reactor, 22 Switching element, 23 Backflow prevention Element, 30 Smoothing capacitor, 40 Inverter circuit, 51 DC bus voltage detection unit, 52 Motor current detection unit, 53 Reactor current detection unit, 60 Inverter control unit, 70 Boost control unit, 74a Target voltage setting unit, 74b Voltage command value calculation Means, 74c current command value calculating means, 74d switching signal generating means, 80 target rotational speed calculating means, 90 boosting operation start determining means, 100 boosting operation stop determining means, 200 air conditioner.

Claims (11)

A rectifier that rectifies the AC voltage supplied from the AC power supply;
A booster circuit that has a reactor, a switching element, and a backflow prevention element, and boosts the DC bus voltage supplied from the rectifier;
A smoothing capacitor for smoothing the output of the booster circuit;
An inverter circuit that converts the DC bus voltage smoothed by the smoothing capacitor into an AC voltage and supplies the AC voltage to the motor;
Boost control means for controlling the operation of the boost circuit;
Inverter control means for controlling the operation of the inverter circuit;
A DC bus voltage detector for detecting a DC bus voltage supplied from the booster circuit,
The step-up control means performs a step-up operation start operation or a stop operation based on the modulation degree of conversion from the DC bus voltage to the AC voltage in the inverter control means,
When the DC bus voltage supplied from the booster circuit is increasing while the booster control unit causes the booster circuit to perform the boosting operation , the inverter control unit sets the set rotational speed of the motor. Operating the inverter circuit to be fixed,
Motor drive control device. Said boost control means, based on the degree of modulation start operation of the boost operation is stored at the time of complete, it performs the stopping operation of the boosting operation,
The motor drive control device according to claim 1 . The step-up control means performs a stop operation of the step-up operation based on the set rotational speed of the motor stored simultaneously with the stored modulation degree ;
The motor drive control device according to claim 2 . The step-up control means starts the step-up operation when the degree of modulation exceeds a predetermined value;
The motor drive control apparatus of any one of Claims 1-3.   The step-up control means performs a start-up operation of the step-up operation based on a set rotational speed of the motor;
The motor drive control apparatus of any one of Claims 1-4. The step-up control unit changes the amount of change per unit time of the DC bus voltage supplied from the step-up circuit while the step-up circuit starts the step-up operation or stops the step-up operation. To set,
The motor drive control apparatus as described in any one of Claims 1-5 . At least one of the switching element and the backflow prevention element is made of a wide band gap semiconductor,
The motor drive control apparatus as described in any one of Claims 1-6 . The wide band gap semiconductor is a silicon carbide element, a gallium nitride-based element, or a diamond element.
The motor drive control device according to claim 7 . The motor drive control device according to any one of claims 1 to 8 ,
A motor driven by the motor drive control device;
With compressor. The motor drive control device according to any one of claims 1 to 8 ,
A motor driven by the motor drive control device;
Blower equipped with. The motor drive control device according to any one of claims 1 to 8 ,
A motor driven by the motor drive control device;
Air conditioner with

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